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From: Matthew Wilcox <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-xfs@vger.kernel.org,
	William Kucharski <william.kucharski@oracle.com>,
	linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com,
	linux-mm@kvack.org, ocfs2-devel@oss.oracle.com,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-erofs@lists.ozlabs.org, Christoph Hellwig <hch@lst.de>,
	linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v11 05/25] mm: Add new readahead_control API
Date: Wed, 15 Apr 2020 04:22:16 -0700
Message-ID: <20200415112216.GC5820@bombadil.infradead.org> (raw)
In-Reply-To: <20200414215616.f665d12f8549f52606784d1e@linux-foundation.org>

On Tue, Apr 14, 2020 at 09:56:16PM -0700, Andrew Morton wrote:
> On Tue, 14 Apr 2020 19:18:08 -0700 Matthew Wilcox <willy@infradead.org> wrote:
> > Hmm.  They don't seem that big to me.
> 
> They're really big!

v5.7-rc1:	11636	    636	    224	  12496	   30d0	fs/iomap/buffered-io.o
readahead_v11:	11528	    636	    224	  12388	   3064	fs/iomap/buffered-io.o

> > __readahead_batch is much bigger, but it's only used by btrfs and fuse,
> > and it seemed unfair to make everybody pay the cost for a function only
> > used by two filesystems.
> 
> Do we expect more filesystems to use these in the future?

I'm honestly not sure.  I think it'd be nice to be able to fill a bvec
from the page cache directly, but I haven't tried to write that function
yet.  If so, then it'd be appropriate to move that functionality into
the core.

> > > The code adds quite a few (inlined!) VM_BUG_ONs.  Can we plan to remove
> > > them at some stage?  Such as, before Linus shouts at us :)
> > 
> > I'd be happy to remove them.  Various reviewers said things like "are you
> > sure this can't happen?"
> 
> Yeah, these things tend to live for ever.  Please add a todo to remove
> them after the code has matured?

Sure!  I'm touching this code some more in the large pages patch set, so
I can get rid of it there.

  reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-14 15:02 [PATCH v11 00/25] Change readahead API Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox
2020-04-15  9:10   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 02/25] mm: Return void from various readahead functions Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 03/25] mm: Ignore return value of ->readpages Matthew Wilcox
2020-04-15  9:17   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox
2020-04-15  9:19   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 05/25] mm: Add new readahead_control API Matthew Wilcox
2020-04-15  1:17   ` Andrew Morton
2020-04-15  2:18     ` Matthew Wilcox
2020-04-15  4:56       ` Andrew Morton
2020-04-15 11:22         ` Matthew Wilcox [this message]
2020-04-14 15:02 ` [PATCH v11 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox
2020-04-15  9:30   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox
2020-04-15  9:31   ` Johannes Thumshirn
2020-04-14 15:02 ` [PATCH v11 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 11/25] mm: Add readahead address space operation Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 14/25] mm: Document why we don't set PageReadahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 18/25] erofs: Convert uncompressed files " Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 19/25] erofs: Convert compressed " Matthew Wilcox
2020-04-21  5:42   ` Andrew Morton
2020-04-21  7:28     ` Gao Xiang via Linux-erofs
2020-04-14 15:02 ` [PATCH v11 20/25] ext4: Convert " Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox
2020-04-14 15:02 ` [PATCH v11 24/25] fuse: Convert from readpages to readahead Matthew Wilcox
2020-04-20 11:14   ` Miklos Szeredi
2020-04-20 11:43     ` Matthew Wilcox
2020-04-20 11:54       ` Miklos Szeredi
2020-04-14 15:02 ` [PATCH v11 25/25] iomap: " Matthew Wilcox

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